Coast Of Central Chile Research Articles

A multi-proxy reconstruction of depositional environment of a Late Pleistocene submerged site from the Central Coast of Chile (32°): Implications for drowned sites

Site GNL Quintero 1 (GNLQ1), located on the central Chilean coast (32°S), remains the only submerged fini-Pleistocene landscape reported for the southeastern Pacific coast to date. This unique site is characterized by a high frequency and diversity of extinct terrestrial faunal remains supported within a fine-grained sedimentary matrix. Several studies have been performed on the faunal assemblage; however, the sedimentary environment in which the site was formed still remains unclear. In this work, stratigraphic, sedimentological and geochemical analyses conducted on two marine cores are combined with seismic data to determine the depositional conditions affecting the formation of this exceptional shallowly buried submerged landscape. Previous results indicated that site GNLQ1 formed, at least between 28 and 21 ka, in an aquifer-fed freshwater lagoon that developed on a fluvial plain. Here, we show a three-stage sedimentological evolution. In the first stage, a shallow restricted freshwater lagoon formed under relatively arid conditions. Subsequently, the lagoon expanded and deepened under the humid climatic conditions that affected central Chile during the Last Glacial Maximum (LGM). Finally, around 8.5-8 ka, the most recent post-glacial marine transgression (PMT) submerged the site, probably eroding the Late Pleistocene – Early Holocene part of the sequence. Currently, the site lies at ca. 13 m b.s.l. within the shoreface of present-day Quintero Bay, 650 m from the current shoreline. This enhanced understanding of GNLQ1's evolution offers a new perspective on resource availability on the coastal shelf of western South America during the Late Pleistocene, as well as highlighting the unexpected paleontological potential of this area and encouraging future archaeological research of potential prehistoric evidence within these drowned landscapes.

Mineral species and formation processes: Raman spectroscopic and microscopic analysis of stains from a late pleistocene continental drowned faunal bone assemblage, Central Chile

AbstractIn this study we address the analysis of bone staining and its sedimentary deposits to obtain a better understanding of the taphonomic trajectories of faunal assemblages in dynamic site formation processes. The fossil remains belong to continental fauna recovered at GNL Quintero 1, a Late Pleistocene drowned terrestrial site located nearshore at Quintero bay in the central coast of Chile (32° S). By conducting Raman spectroscopic and microscopic analyses we aim to identify the mineral compounds of bone staining and their sedimentary matrix, perform a first geochemical characterization of the depositional environments and carry out paleoenvironmental inferences. Stains are present on most remains and recur in a variety of colors, indicating the presence of minerals, such as hematite, goethite, pyrolusite, pyrite or marcasite, mackinawite, and greigite. Mineral species identified are associated with oxic and anoxic environments, suggesting that the bones and sediments underwent both sulfuricization and sulfidization processes. Spectroscopic data obtained suggest that the trajectory of the remains was much more dynamic than previously assumed. These geochemical scenarios of alternating oxidation and reduction reflects the diverse environments involved during the terrestrial phase, the transitional phase of rising sea level, and subsequently the marine phase.

Local and remote physical processes driving variability of the planktonic system in the Juan Fernández Archipelago: A multidisciplinary framework providing conservation insights

Abstract The Juan Fernandez Ridge, a vulnerable marine ecosystem located far off the coast of central Chile and formed by several seamounts, guyots and three islands (Robinson Crusoe, Santa Clara and Alejandro Selkirk), has recently been declared a Coastal Marine Protected Area of Multiple Uses with several National Parks embedded in it. Recent studies have highlighted the influence of remote and local oceanographic structures on the hydrographic dynamics of this ridge. However, there is still a gap in understanding how they affect the structure and dynamics of the surrounding insular planktonic communities. A hydroacoustic and oceanographic survey was conducted during the austral spring (October 2016), including hydrographic and zooplankton sampling around Robinson Crusoe Island. Oceanographic features were identified and tracked using satellite data (chlorophyll‐a (Chl‐a) and sea surface temperature) and modelling results. Two events of Chl‐a increase relative to a threshold (>0.45 mg m−3) were forced by different physical processes, both affecting the western side of Robinson Crusoe Island. In event A during the cruise period, Chl‐a subsurface maxima were associated with the arrival of a coastal meander originating on the continental shelf off Chile (remote process); the zooplankton was dominated by copepods and salps, with an evident coastal–oceanic gradient. In event B, Chl‐a maxima were linked to a local upwelling forced by the intensification of a localized SSW wind. No influence of remote eddies or local Von Kármán vortices on Chl‐a distribution was observed. These findings highlight the influence of remote and local physical processes on the structure of planktonic communities around Robinson Crusoe Island. Understanding the variability of these mechanisms and their effects at the base of the pelagic food web is critical in adopting an ecosystem‐level approach.

Connecting spatial structure in subtidal benthic communities with temporal variability in bottom temperature and dissolved oxygen along an upwelling coast

While spatial patterns in the structure of intertidal communities have been linked to changes in surface-ocean conditions indicative of coastal advection, nutrient supply, and productivity, less is known as to environmental features that, in addition to substrate type, are most influential in structuring subtidal benthic communities. Here we analyze data from subtidal benthic surveys conducted at six sites spanning ca. 180 km of shoreline along the upwelling coast of central Chile. Using continuous records of temperature and dissolved oxygen in bottom waters from each site, we tested whether among-site differences in community structure can be better explained by considering features of local environmental variability in addition to changes in substrate type. Starting from the NMDS ordination of benthic sites based on the presence and relative abundance of 29 species, we used PERMANOVA to test the explanatory power of substrate type and nine indices of environmental variability derived from in situ records. Three indices, namely the high-frequency variability and 95th percentile of bottom temperatures together with an index for the duration of hypoxia events, explained individually as much of the total variance as substrate type alone (ca. 30%). When combined into a single PERMANOVA analysis, these four factors explained 84% of the total variance in the NMDS-based ordination of benthic communities across the study region. A comparison of the benthic species ordination and environment-based site ordination suggests that soft-bottom species such as the razor clam Ensis macha, the snail Chorus giganteus, and the crab Cancer setosus, might be physiologically more tolerant to more rigorous conditions in terms of more intense warming and longer hypoxia events. Hard bottom species such as the gastropods Concholepas concholepas and Fissurella sp. and the barnacle Austromegabalanus psittacus thrive in environments where the temperature is lower on average but highly variable and where hypoxic conditions are intense but more intermittent. Our findings highlight the structuring role of the variability and the occurrence of extreme conditions, rather than the most frequent levels, in bottom-water properties such as temperature and dissolved oxygen. These two properties are closely intertwined in this and other coastal upwelling regions and are susceptible to change widely under future climate scenarios.

Future Changes in the Free Tropospheric Freezing Level and Rain–Snow Limit: The Case of Central Chile

The freezing level in the free troposphere often intercepts the terrain of the world’s major mountain ranges, creating a rain–snow limit. In this work, we use the free tropospheric height of the 0 °C isotherm (H0) as a proxy of both levels and study its distribution along the western slope of the subtropical Andes (30°–38° S) in present climate and during the rest of the 21st century. This portion of the Andes corresponds to central Chile, a highly populated region where warm winter storms have produced devastating landslides and widespread flooding in the recent past. Our analysis is based on the frequency distribution of H0 derived from radiosonde and surface observations, atmospheric reanalysis and climate simulations. The future projections primarily employ a scenario of heavy greenhouse gasses emissions (RCP8.5), but we also examine the more benign RCP4.5 scenario. The current H0 distribution along the central Chile coast shows a gradual decrease southward, with mean heights close to 2600 m ASL (above sea level) at 30 °C S to 2000 m ASL at 38° S for days with precipitation, about 800 m lower than during dry days. The mean value under wet conditions toward the end of the century (under RCP8.5) is close to, or higher than, the upper quartile of the H0 distribution in the current climate. More worrisome, H0 values that currently occur only 5% of the time will be exceeded in about a quarter of the rainy days by the end of the century. Under RCP8.5, even moderate daily precipitation can increase river flow to levels that are considered hazardous for central Chile.

Coastal pollution from the industrial park Quintero bay of central Chile: Effects on abundance, morphology, and development of the kelp Lessonia spicata (Phaeophyceae).

The industrial park of Quintero Bay (QB) in the central coast of Chile was established in the 1960s, presents high levels of pollution due to the industrial activity, and it is known as one of the five Chilean “sacrifice zones”. Lessonia spicata is the most important habitat-forming kelp species in the intertidal along the central and south shores of Chile, and currently there are no morphometric and population studies of L. spicata (or other seaweed species) nor studies about the effects of pollution on its development in QB and neighbouring sites. In this context, the aims of this study were (i) to register the abundance and morphological features of L. spicata populations from Ventanas, Horcón and Cachagua (sites with different pollution histories and located only up to 40 km from the QB); ii) to determine the heavy metals (HMs) concentration in seawater and marine sediments; and (iii) to evaluate in vitro the effects of exposure to seawater from the three sampling sites on spore release and early developmental stages, up to the juvenile sporophyte. Results showed that the chronically exposed Ventanas kelp population had the smallest adult individuals in comparison with the other sites. Ventanas and Horcón registered high HMs concentration in the seawater and marine sediments exceeding the international permissible limits (e.g in seawater Cu 20–859 μg L-1; sediments Cu > 50,000 μg kg-1). Unexpectedly in Cachagua, a site often considered unpolluted, high concentrations of Cu and As were also registered in the seawater (859 and 1,484 μg L-1, respectively) and of As in marine sediments (20,895 μg kg-1). Exposure of gametophytes to the seawater from Ventanas resulted in a developmental delay compared to the other treatments; however, low sporophyte production was determined in all treatments. Our results indicate that QB, more notably Ventanas, induce highly negative effects on individual development, and consequently on seaweed populations, which suggest a long-term negative impact on the community structure of these marine zones. Furthermore, the high concentrations of HMs reported here at Cachagua suggest a recent expansion of pollution along the central coast of Chile, evidencing effects on the marine ecosystem health even on sites far from the pollution source.

First detection of pectenotoxin-2 in shellfish associated with an intense spring bloom of Dinophysis acuminata on the central Chilean coast

Diarrhetic shellfish poisoning (DSP) toxins and pectenotoxins (PTX) produced by endemic species of the genus Dinophysis, mainly D. acuta and D. acuminata, pose a big threat to public health, artisanal fisheries and the aquaculture industry in Southern Chile. This work reports the first detection of lipophilic toxins, including pectenotoxin-2 (PTX-2) and gymnodimine-A (GYM-A), in hard razor clam (Tagelus dombeii) associated with an unprecedented spring bloom −38.4 × 103 cells L−1 in integrated hose sampler (0–10 m) – of Dinophysis acuminata in coastal waters of central Chile. The socio-economic challenges to small-scale fisheries are discussed. The study points to the pressing need for sound policies to face unexpected HAB event, probably due to biogeographical expansions, with a focus on fisheries management, participation of stakeholders, and development of adaptive capacities.

Exposure to Toxoplasma gondii in Marine Otters (Lontra felina) and Domestic Cats (Felis catus) in an Arid Environment in Chile.

Toxoplasma gondii is a worldwide-distributed protozoon that infects warm-blooded animals. We determined T. gondii exposure in one marine otter (Lontra felina) and four domestic cats (Felis catus) along the northern and central coast of Chile, indicating a low seroprevalence of 5% (1/19) and 8% (4/50) respectively, likely related to arid environment.

Integration of biophysical connectivity in the spatial optimization of coastal ecosystem services

Ecological connectivity in coastal oceanic waters is mediated by dispersion of the early life stages of marine organisms and conditions the structure of biological communities and the provision of ecosystem services. Integrated management strategies aimed at ensuring long-term service provision to society do not currently consider the importance of dispersal and larval connectivity. A spatial optimization model is introduced to maximise the potential provision of ecosystem services in coastal areas by accounting for the role of dispersal and larval connectivity. The approach combines a validated coastal circulation model that reproduces realistic patterns of larval transport along the coast, which ultimately conditions the biological connectivity and productivity of an area, with additional spatial layers describing potential ecosystem services. The spatial optimization exercise was tested along the coast of Central Chile, a highly productive area dominated by the Humboldt Current. Results show it is unnecessary to relocate existing management areas, as increasing no-take areas by 10% could maximise ecosystem service provision, while improving the spatial representativeness of protected areas and minimizing social conflicts. The location of protected areas was underrepresented in some sections of the study domain, principally due to the restriction of the model to rocky subtidal habitats. Future model developments should encompass the diversity of coastal ecosystems and human activities to inform integrative spatial management. Nevertheless, the spatial optimization model is innovative not only for its integrated ecosystem perspective, but also because it demonstrates that it is possible to incorporate time-varying biophysical connectivity within the optimization problem, thereby linking the dynamics of exploited populations produced by the spatial management regime.

Worst-case tsunami scenario in Cartagena Bay, central Chile: Challenges for coastal risk management

Tsunami risk is analyzed regarding a probable extreme event in Cartagena Bay (33°S), one of the most anthropized areas of Chile and part of its main metropolitan area. An event with characteristics similar to those of the 1730 earthquake (Mw 9.1) was modelled considering the worst-case scenario for the coast of central Chile. Vulnerability is analyzed by applying the Social Vulnerability Index (SoVI) with representative census (2017) variables. A principal component analysis (PCA) was applied to the variables, generating 8 main groups. The results established flooding heights up to 9 m with maximum flow velocities of 10 m/s. The first inundation started 5 min after the earthquake but consecutive hazardous waves were active for at least 6 h after the shaking. Social vulnerability was established as high for the components that made up the following variables: socioeconomic status, housing material, access to basic services and gender, which are directly related to the occupancy, promoted by planning instruments, of dune fields and the periphery of wetlands. The risk area encompasses 99% of the affected area, while 67.5% of the area is at high risk. Mitigation and prevention measures that can be addressed in territorial planning and coastal management are proposed, prioritizing the restoration of the dune system as a natural protection measure against extreme events, the relocation of the population in irregular occupancy conditions, evaluation of tsunami evacuation potential, planning urban design in conjunction with evacuation routes and consideration of vertical evacuation implementation.

Numerical wave propagation study of the unusual response of Nevados de Chillán volcano to two aftershocks of the 2010 MW = 8.8 Maule earthquake

In 2012, two large aftershocks of the MW = 8.8 Maule, Chile earthquake occurred near the Central Chilean coast. Both events, with magnitudes MW = 6.1 and MW = 7.1 were located about 200 km away from the volcanic/hydrothermal Nevados de Chillán (NdC) complex. The system responded with a significant increase in seismicity to the MW = 6.1 event, and with a reduction in seismicity following the latter, larger MW = 7.1 earthquake. To understand the physical changes induced by both earthquakes at the NdC, we set up a numerical wave propagation study. Our results show that these observations likely result from dynamic changes at the NdC complex during the passage of the seismic waves. In the case of the MW = 6.1 aftershock, the extensive stress transfer was large enough to induce changes at the hydrothermal system, which could have later led to an increase in fluid-driven seismicity. In the case of the MW = 7.1 earthquake, the oblique arrival of seismic waves to the main fault of the NdC due to the MW = 7.1 earthquake induced slight compressions at the reservoir and created openings in the main fault, promoting fluid migration, which can explain the reduction in seismicity beneath the main craters of the volcano. Results also show that the geometry of an underlying fault system can influence the volumetric response, suggesting that the role of local structures in earthquake-volcano interactions influence the behavior of triggered systems and should therefore not be disregarded.

Comparison of QuikSCAT, WRF and buoy ocean surface wind data off Valparaiso Bay, Chile

Abstract The winds that affect the surface of the ocean are also important for a vast array of activities, either operational or scientific, hence the importance of being able to adequately predict this quality. Because of the preceding fact, a Weather Research and Forecasting model was used to perform simulations at the surface of the Ocean, for winds derived from different boundary conditions (NCEP-CFSR, ERA-Interim and NCEP-FNL) and configured with different spatial resolution (25, 5 and 1 km), with the objective of evaluating which of these data sets delivers the more precise wind simulation at the surface of the ocean. A comparative analysis was performed between the different outputs of the WRF model, QuikSCAT satellite and in situ observations of a buoy installed off the central coast of Chile. The results showed that the WRF model, overestimates the wind magnitudes, across all boundary conditions or spatial resolution. Additionally, depending on the in situ wind magnitude (>6 ms−1), the model predicts adequately wind magnitude and direction. Spatial comparisons were performed between QuikSCAT and WRF outputs at the Chilean coast to evaluate any possible differences. The modeled winds showed a tendency to be stronger than those measured by Satellites and the bigger differences appeared closer to the shore. The wavelet coherence and phase analysis, confirmed that the model delivers precise wind information for frequencies greater than the daily cycle. Finally, the results of the simulation produced by the ERA-Interim analysis showed lower errors in terms of temporal and spatial variability of surface winds.

Advanced determination of the spatial gradient of human health risk and ecological risk from exposure to As, Cu, Pb, and Zn in soils near the Ventanas Industrial Complex (Puchuncaví, Chile)

The townships of Puchuncaví and Quintero, on the coast of central Chile, have soils contaminated by atmospheric deposition of sulfur dioxide and trace elements from the nearby Ventanas Industrial Complex. The purpose of this study was to evaluate potential human health and ecological risks, by determining the spatial distribution of soil total concentrations arsenic (As), copper (Cu), lead (Pb), and zinc (Zn) in these townships. Total concentrations of these elements were determined in 245 topsoil samples, used to generate continuous distribution maps. The background concentrations of Cu, As, Pb, and Zn in the studied soils were 100, 16, 35, and 122 mg kg−1, respectively. The concentrations of Cu, As, and Pb were positively correlated with each other, suggesting that their source is the Ventanas copper smelter. On the other hand, correlations for Zn were weaker than for other trace elements, suggesting low impact of the Ventanas copper smelter on spatial distribution of Zn. Indeed, only 6% of the study area exhibited Zn concentrations above the background level. In contrast, 77, 32 and 35% of the study area presented Cu, As, and Pb concentrations, respectively, above the background level. The carcinogenic risk due to exposure to As was above the threshold value of 10−04 in the population of young children (1–5 years old) on 27% of the study area. These risk values are classified as unacceptable, which require specific intervention by the Chilean government. Based on the estimated concentrations of exchangeable Cu, 10, 15, and 75% of the study area exhibited high, medium, and low phytotoxicity risk, respectively.

Predicting the potential distribution of the endemic seabird Pelecanus thagus in the Humboldt Current Large Marine Ecosystem under different climate change scenarios.

BackgroundThe effects of global climate change on species inhabiting marine ecosystems are of growing concern, especially for endemic species that are sensitive due to restricted distribution. One method employed for determining the effects of climate change on the distribution of these organisms is species distribution modeling.MethodsWe generated a model to evaluate the potential geographic distribution and breeding distribution of the Peruvian pelican (Pelecanus thagus). Based on maximum entropy modeling (MaxEnt), we identified the environmental factors that currently affect its geographic distribution and breeding. Then we predicted its future distribution range under two climate change scenarios: moderate (rcp 2.6) and severe (rcp 8.5).ResultsThe mean daytime temperature range and marine primary productivity explain the current potential distribution and breeding of the pelican. Under the future climate change scenarios, the spatial distribution of the pelican is predicted to slightly change. While the breeding distribution of the pelican can benefit in the moderate scenario, it is predicted to decrease (near −20 %) in the severe scenario.DiscussionThe current potential geographic distribution of the pelican is influenced to a large extent by thermal conditions and primary productivity. Under the moderate scenario, a slight increase in pelican breeding distribution is predicted. This increase in habitable area is explained by the climatic conditions in southern Chile, and those climatic conditions will likely be similar to the current conditions of the central coast of Chile. We predict that the coasts of southern Chile will constitute an important refuge for the conservation of the Peruvian pelican under future climate change scenarios.

Impacts of reduced inorganic N:P ratio on three distinct plankton communities in the Humboldt upwelling system

The ratio of inorganic nitrogen to phosphorus (NP) is projected to decrease in the Eastern Boundary Upwelling Systems (EBUS) due to warming of the surface waters. In an enclosure experiment, we employed two levels of inorganic NP ratios (10 and 5) for three distinct plankton communities collected along the coast of central Chile (33°S). The primary effect of the NP treatment was related to different concentrations of NO3, which directly influenced the biomass of phytoplankton. In addition, low inorganic NP ratio reduced the seston NP and Chl a-C ratios, and there were some effects on the plankton community composition, e.g., benefitting Synechococcus spp. in some communities. One of the communities was clearly top-down controlled and trophic transfer to grazers was up to 5.8% during the 12 day experiment. Overall, the initial, natural plankton community composition was more important for seston stoichiometry and trophic transfer than the manipulation of the inorganic NP ratio, highlighting the importance of plankton community structure for marine ecosystem functioning.

Subsurface Mesoscale Eddy Generation in the Ocean off Central Chile

AbstractOff the coast of central Chile, subsurface anticyclonic eddies are a salient feature of the oceanic circulation, transporting a significant fraction of coastal water that is rich in nutrients and poor in dissolved oxygen offshore. In this study, the formation mechanism of these eddies is analyzed through a high‐resolution (~0.3 km) and low‐resolution (~3 km) oceanic model that realistically simulate the regional mean circulation, including the Peru‐Chile Undercurrent (PCUC). An analysis of the vorticity and eddy kinetic energy in both simulations indicated that the subsurface eddies can be triggered through a combination of processes that are associated with instabilities of the PCUC. In the high‐resolution simulation, we observed that the interaction between the PCUC and topographic slope generates anticyclonic vorticity and potential vorticity close to zero in the bottom boundary layer. The separation of the undercurrent from the slope favors the intensification of anticyclonic vorticity. It reaches magnitudes that are larger than the planetary vorticity while kinetic energy is converted from the PCUC to the eddy flow. These processes set the necessary conditions for the development of centrifugal instabilities, which can form submesoscale structures. The coalescence of submesoscale structures generates a subsurface anticyclonic mesoscale eddy. In the low‐resolution simulations (>3 km) centrifugal instabilities are not simulated, and the barotropic conversion of the mean kinetic energy into eddy kinetic energy appears as the main process of eddy formation. We showed that the vertical structure of these eddies is sensitive to the spatial resolution of the model.

Tsunami Modeling and Satellite-Based Emergency Mapping: Workflow Integration Opportunities

Satellite-based Emergency Mapping (SEM) mechanisms provide information for emergency response in relation to different types of disasters, including tsunamis, based on the analysis of satellite imagery acquired in the aftermath of an event. One of the main critical aspects of a SEM service is the timeliness in providing relevant information in the hours following the event. The availability of a relevant post-event image is crucial; therefore, satellite sensors need to be programmed as soon as possible. The integration of a tsunami alerting system, like the one offered by the Global Disaster Alert and Coordination System (GDACS), can be highly beneficial in a SEM mechanism for streamlining and accelerating the satellite programming task and for generating first damage estimates. The GDACS tsunami model is validated using tidal gauge data and a post-event field survey. Tsunami model outputs are then exploited to automatically identify areas of interest to be used for immediate satellite acquisition triggering. Three alternative operational integration approaches are proposed, described and discussed, taking as use case the tsunami that struck the central Chilean coast after the 8.3 magnitude earthquake on 16 September 2015.

Genetic structure analysis of Girella laevifrons populations in central Chile

Connectivity among most marine species depends of their life cycles, and the main phase that can regulate dispersal is the larval stage of an organism. Girella laevifrons (Girellidae) is an omnivore fish inhabiting in intertidal pools as juveniles and subtidal reefs as adults from northern to central Chile. It has a pelagic larval duration for approximately 69 days. In this study, we used eight molecular markers (microsatellites) to explore the genetic structure of their populations along 400 km of the central Chilean coast.20 juveniles were sampled from four different populations. Microsatellite loci did not detect a genetic structure within a 400 km scale along the coast of Central Chile. There is evidence (Fst = −0.0038, p = 0.8954) suggesting that populations between Coquimbo and Littoral Central behave as a single whole population. This could be an estimate that may define future management units for the species.

Active Commuting to University and its Association with Sociodemographic Factors and Physical Activity Levels in Chilean Students.

Background and Objectives: Active commuting to and from university (ACU) could be a strategy to increase physical activity levels (PA) and promote health in young university students. We aimed to a) examine the patterns of commuting to university in Chilean students; b) the association between the mode of commuting to and from university and socio-demographic factors and PA-levels. Materials and Methods: A total of 496 university students (21.6 ± 2.4 years old) from two universities from Valparaíso (central coast of Chile) participated in this study. Personal data, home address, socio-economic status, PA, and the usual mode of commuting to and from the university were self-reported by a questionnaire. The commute distances were objectively measured using Google-Maps-software. Associations were examined using binary logistic regressions. Results: The main mode of commuting was by bus (to university: 55.2% vs. from university: 59.3%; p < 0.001). The least used mode was cycling (1.4% to and from university). Students living >5-km from university were less active commuters than those living in closer distances: (2–5 km, odds ratio (OR): 4.424, 95% and 95% confidence intervals (CI): 2.443–8.011, p < 0.001; 2 km, OR: 143.052, 95% CI: 55.154–371.030, p < 0.001). Students with low PA-levels were less active commuters than those with medium (OR: 1.446; 95% CI: 0.864–2.421; p = 0.160) or higher levels (OR: 1.880; 95% CI: 1.880–1.094; p = 0.022). Students who lived between 2 and 5 km, presented a significant association to be active commuters when they showed medium PA-levels (OR: 5.244, 95% CI: 1.358–20.246; p = 0.016). Conclusions: Chilean university students from Valparaíso are mainly passive commuters using public transport as the main mode of commuting to and from university; longer distances from home to the university are associated with low PA levels. ACU in distances between 2–5 km (mainly walking) could contribute to having medium PA-levels in Chilean university students. Thus, promoting the ACU walking to and from the university in such distances could be an effective strategy to increase the overall PA levels in Chilean university students.

Multi‐millennial scale climate variability during MIS 3 and MIS 2 inferred from luminescence dating of coastal sand dunes and buried paleosol sequences in central Chile, 32°S

ABSTRACTThe eolian morphostratigraphic archive along the coast of central Chile (∼37–30°S) includes sand dune and buried paleosol sequences that despite their potential as a proxy for past environmental change, remain mostly unstudied north of Patagonia and south of the Atacama Desert core. Here, we present results of a stratigraphic and geochronologic study using the post‐infrared infrared stimulated luminescence signal stimulated at 225 °C (pIRIR225) of potassium‐rich feldspar that show the timing of past climate variability as evidenced from sand dune/buried paleosol couplets at 32°S. Our record shows that periods of sand dune accumulation during Marine Isotope Stages MIS 6, 4, 3 and 2 occurred within ice ages and associated low sea‐level stands, probably affected by similar to, or drier than, present conditions. Intercalated wetter periods inferred from pedogenesis occurred between 53 ± 4 and 52 ± 3 ka, at some time between 52 ± 3 and 36 ± 2 ka, and at some time between 31 ± 2 and 22 ± 2 ka, and reflect times when the southern westerlies rain belt shifted north. Our data reveal that central Chile experienced multi‐millennial periodicity of westerly precipitation throughout the last glacial period. We provide evidence for a humid local Last Glacial Maximum.